/* acos example */
#include <stdio.h>
#include <math.h>

#define PI 3.14159265

int main()
{
  double param, result;
  param = 0.5;
  result = acos(param) * 180.0 / PI;
  printf("The arc cosine of %lf is %lf degrees.\n", param, result);
  return 0;
}